The invention relates to a knee airbag for a vehicle occupant restraint device. The invention further relates to a vehicle occupant restraint device comprising such knee airbag.
The inflation and exhaust behavior of airbags is tested with crash test dummies during impact tests. Crash test dummies are life-size dolls imitating the human body. In order to duly consider the different anatomic conditions of real persons during simulations, the tests are usually carried out with three different dummies: The “50 percent male” having a body height of 175 cm and a weight of 78 kg is supposed to correspond in general to a “normally” sized vehicle occupant, the “95 percent male” having a body height of 188 cm and a weight of 101 kg is supposed to correspond to a tall vehicle occupant and the “5 percent female” having a body height of 152 cm and a weight of 54 kg is supposed to correspond to a short vehicle occupant. Due to the different constitution, in the crash tests the normal seating positions of the different dummies vary accordingly.
From DE 10 2004 009 013 A1 a side impact restraint device for the protection of an occupant seated on a vehicle seat in a vehicle comprising an airbag is known which adapts to the build of the vehicle occupant. The airbag deploys between a side structure of the vehicle and the vehicle occupant and includes a first exhaust orifice disposed in an area of the airbag facing the vehicle occupant. The vertical position of the exhaust orifice is selected so that it is not covered by the upper body part of a short vehicle occupant, but that it is covered by a tall vehicle occupant. Thus for a short vehicle occupant a lower internal pressure is provided in the airbag than for a tall vehicle occupant.
In EP 1 279 565 A1 a generic knee airbag for an occupant protection device is shown in which a venting hole is provided in an upper end portion. The venting hole interacts with a passenger airbag disposed above the knee airbag. When the legs of the vehicle occupant hit the deployed knee airbag and the venting hole initially is not yet covered by the passenger airbag, gas can exhaust from the venting hole. In this way the impact exerted on the vehicle occupant is dampened. As soon as the deployed passenger airbag covers the venting hole, however, the gas discharge from the venting hole is restricted so that a minimum internal pressure of the knee airbag is retained for a longer period of time.